One day Yao-shan Wei-yen (750-834), one of the well-known Chinese Ch'an master, was asked by the host of the monastery to give his sermon to the assembly who for a long while was expecting his teaching. Yao-shan said: "Strike the bell."
Kinhin (Jap.) You can do walking zazen after each time you do sitting zazen to refresh your body, lessen the feeling of numbness or sleepiness. You feel bored or tired because you are not some kind of machine which works at the same speed whole day and night.
Your continued practice from sitting to walking and from walking back to sitting means that if you do breath counting, for instance, keep going with it.
In walking zazen, you place your right fist with the thumb inside, on your chest and your left palm covers the right fist, with both elbows held to make right angles with your body. Your eyes rest at a point about two yards in front of the feet.
Start stepping forward with the left foot first. Your heel down to the floor first then the toes, step like your foot sinks into the floor. Do each step about 6 inches forward slowly with your breath in and out and with mindfulness.
You can walk briskly and with energy like a Rinzai does, or you can walk slowly and leisurely as a Soto does. Your walk might make a wide circle or a rectangle, it depends on the site you have. Each time will be about five to ten minutes after each sitting of twenty five to forty-five minutes.